/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   https://www.lammps.org/, Sandia National Laboratories
   LAMMPS development team: developers@lammps.org

   Copyright (2003) Sandia Corporation.  Under the terms of Contract
   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
   certain rights in this software.  This software is distributed under
   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */

/* ----------------------------------------------------------------------
   Contributing author: Trung Dac Nguyen (ORNL)
------------------------------------------------------------------------- */

#include "pair_lj_sf_dipole_sf_gpu.h"

#include "atom.h"
#include "domain.h"
#include "error.h"
#include "force.h"
#include "gpu_extra.h"
#include "neigh_list.h"
#include "neighbor.h"
#include "suffix.h"
#include "update.h"

#include <cmath>
#include <cstring>

using namespace LAMMPS_NS;

// External functions from cuda library for atom decomposition

int dplsf_gpu_init(const int ntypes, double **cutsq, double **host_lj1, double **host_lj2,
                   double **host_lj3, double **host_lj4, double *special_lj, const int nlocal,
                   const int nall, const int max_nbors, const int maxspecial,
                   const double cell_size, int &gpu_mode, FILE *screen, double **host_cut_ljsq,
                   double **host_cut_coulsq, double *host_special_coul, const double qqrd2e);
void dplsf_gpu_clear();
int **dplsf_gpu_compute_n(const int ago, const int inum, const int nall, double **host_x,
                          int *host_type, double *sublo, double *subhi, tagint *tag, int **nspecial,
                          tagint **special, const bool eflag, const bool vflag, const bool eatom,
                          const bool vatom, int &host_start, int **ilist, int **jnum,
                          const double cpu_time, bool &success, double *host_q, double **host_mu,
                          double *boxlo, double *prd);
void dplsf_gpu_compute(const int ago, const int inum, const int nall, double **host_x,
                       int *host_type, int *ilist, int *numj, int **firstneigh, const bool eflag,
                       const bool vflag, const bool eatom, const bool vatom, int &host_start,
                       const double cpu_time, bool &success, double *host_q, double **host_mu,
                       const int nlocal, double *boxlo, double *prd);
double dplsf_gpu_bytes();

/* ---------------------------------------------------------------------- */

PairLJSFDipoleSFGPU::PairLJSFDipoleSFGPU(LAMMPS *lmp) : PairLJSFDipoleSF(lmp), gpu_mode(GPU_FORCE)
{
  respa_enable = 0;
  reinitflag = 0;
  cpu_time = 0.0;
  suffix_flag |= Suffix::GPU;
  GPU_EXTRA::gpu_ready(lmp->modify, lmp->error);
}

/* ----------------------------------------------------------------------
   free all arrays
------------------------------------------------------------------------- */

PairLJSFDipoleSFGPU::~PairLJSFDipoleSFGPU()
{
  dplsf_gpu_clear();
}

/* ---------------------------------------------------------------------- */

void PairLJSFDipoleSFGPU::compute(int eflag, int vflag)
{
  ev_init(eflag, vflag);

  int nall = atom->nlocal + atom->nghost;
  int inum, host_start;

  bool success = true;
  int *ilist, *numneigh, **firstneigh;
  if (gpu_mode != GPU_FORCE) {
    double sublo[3], subhi[3];
    if (domain->triclinic == 0) {
      sublo[0] = domain->sublo[0];
      sublo[1] = domain->sublo[1];
      sublo[2] = domain->sublo[2];
      subhi[0] = domain->subhi[0];
      subhi[1] = domain->subhi[1];
      subhi[2] = domain->subhi[2];
    } else {
      domain->bbox(domain->sublo_lamda, domain->subhi_lamda, sublo, subhi);
    }
    inum = atom->nlocal;
    firstneigh = dplsf_gpu_compute_n(
        neighbor->ago, inum, nall, atom->x, atom->type, sublo, subhi, atom->tag, atom->nspecial,
        atom->special, eflag, vflag, eflag_atom, vflag_atom, host_start, &ilist, &numneigh,
        cpu_time, success, atom->q, atom->mu, domain->boxlo, domain->prd);
  } else {
    inum = list->inum;
    ilist = list->ilist;
    numneigh = list->numneigh;
    firstneigh = list->firstneigh;
    dplsf_gpu_compute(neighbor->ago, inum, nall, atom->x, atom->type, ilist, numneigh, firstneigh,
                      eflag, vflag, eflag_atom, vflag_atom, host_start, cpu_time, success, atom->q,
                      atom->mu, atom->nlocal, domain->boxlo, domain->prd);
  }
  if (!success) error->one(FLERR, "Insufficient memory on accelerator");

  if (atom->molecular != Atom::ATOMIC && neighbor->ago == 0)
    neighbor->build_topology();
  if (host_start < inum) {
    cpu_time = platform::walltime();
    cpu_compute(host_start, inum, eflag, vflag, ilist, numneigh, firstneigh);
    cpu_time = platform::walltime() - cpu_time;
  }
}

/* ----------------------------------------------------------------------
   init specific to this pair style
------------------------------------------------------------------------- */

void PairLJSFDipoleSFGPU::init_style()
{
  if (!atom->q_flag || !atom->mu_flag || !atom->torque_flag)
    error->all(FLERR, "Pair dipole/sf/gpu requires atom attributes q, mu, torque");

  if (strcmp(update->unit_style, "electron") == 0)
    error->all(FLERR, "Cannot (yet) use 'electron' units with dipoles");

  // Repeat cutsq calculation because done after call to init_style
  double maxcut = -1.0;
  double cut;
  for (int i = 1; i <= atom->ntypes; i++) {
    for (int j = i; j <= atom->ntypes; j++) {
      if (setflag[i][j] != 0 || (setflag[i][i] != 0 && setflag[j][j] != 0)) {
        cut = init_one(i, j);
        cut *= cut;
        if (cut > maxcut) maxcut = cut;
        cutsq[i][j] = cutsq[j][i] = cut;
      } else
        cutsq[i][j] = cutsq[j][i] = 0.0;
    }
  }
  double cell_size = sqrt(maxcut) + neighbor->skin;

  int maxspecial = 0;
  if (atom->molecular != Atom::ATOMIC) maxspecial = atom->maxspecial;
  int mnf = 5e-2 * neighbor->oneatom;
  int success =
      dplsf_gpu_init(atom->ntypes + 1, cutsq, lj1, lj2, lj3, lj4, force->special_lj, atom->nlocal,
                     atom->nlocal + atom->nghost, mnf, maxspecial, cell_size, gpu_mode, screen,
                     cut_ljsq, cut_coulsq, force->special_coul, force->qqrd2e);
  GPU_EXTRA::check_flag(success, error, world);

  if (gpu_mode == GPU_FORCE) neighbor->add_request(this, NeighConst::REQ_FULL);
}

/* ---------------------------------------------------------------------- */

double PairLJSFDipoleSFGPU::memory_usage()
{
  double bytes = Pair::memory_usage();
  return bytes + dplsf_gpu_bytes();
}

/* ---------------------------------------------------------------------- */

void PairLJSFDipoleSFGPU::cpu_compute(int start, int inum, int eflag, int vflag, int *ilist,
                                      int *numneigh, int **firstneigh)
{
  int i, j, ii, jj, jnum, itype, jtype;
  double qtmp, xtmp, ytmp, ztmp, delx, dely, delz, evdwl, ecoul, fx, fy, fz;
  double rsq, rinv, r2inv, r6inv, r3inv, r5inv;
  double forcecoulx, forcecouly, forcecoulz, crossx, crossy, crossz;
  double tixcoul, tiycoul, tizcoul;
  double fq, pdotp, pidotr, pjdotr, pre1, pre2, pre4;
  double forcelj, factor_coul, factor_lj;
  double presf, afac, bfac, pqfac, qpfac, forceljcut, forceljsf;
  double aforcecoulx, aforcecouly, aforcecoulz;
  double bforcecoulx, bforcecouly, bforcecoulz;
  double rcutlj2inv, rcutcoul2inv, rcutlj6inv;
  int *jlist;

  evdwl = ecoul = 0.0;
  ev_init(eflag, vflag);

  double **x = atom->x;
  double **f = atom->f;
  double *q = atom->q;
  double **mu = atom->mu;
  double **torque = atom->torque;
  int *type = atom->type;
  double *special_coul = force->special_coul;
  double *special_lj = force->special_lj;
  double qqrd2e = force->qqrd2e;

  // loop over neighbors of my atoms

  for (ii = start; ii < inum; ii++) {
    i = ilist[ii];
    qtmp = q[i];
    xtmp = x[i][0];
    ytmp = x[i][1];
    ztmp = x[i][2];
    itype = type[i];
    jlist = firstneigh[i];
    jnum = numneigh[i];

    for (jj = 0; jj < jnum; jj++) {
      j = jlist[jj];
      factor_lj = special_lj[sbmask(j)];
      factor_coul = special_coul[sbmask(j)];
      j &= NEIGHMASK;

      delx = xtmp - x[j][0];
      dely = ytmp - x[j][1];
      delz = ztmp - x[j][2];
      rsq = delx * delx + dely * dely + delz * delz;
      jtype = type[j];

      if (rsq < cutsq[itype][jtype]) {
        r2inv = 1.0 / rsq;
        rinv = sqrt(r2inv);

        // atom can have both a charge and dipole
        // i,j = charge-charge, dipole-dipole, dipole-charge, or charge-dipole

        forcecoulx = forcecouly = forcecoulz = 0.0;
        tixcoul = tiycoul = tizcoul = 0.0;

        if (rsq < cut_coulsq[itype][jtype]) {

          if (qtmp != 0.0 && q[j] != 0.0) {
            pre1 = qtmp * q[j] * rinv * (r2inv - 1.0 / cut_coulsq[itype][jtype]);

            forcecoulx += pre1 * delx;
            forcecouly += pre1 * dely;
            forcecoulz += pre1 * delz;
          }

          if (mu[i][3] > 0.0 && mu[j][3] > 0.0) {
            r3inv = r2inv * rinv;
            r5inv = r3inv * r2inv;
            rcutcoul2inv = 1.0 / cut_coulsq[itype][jtype];

            pdotp = mu[i][0] * mu[j][0] + mu[i][1] * mu[j][1] + mu[i][2] * mu[j][2];
            pidotr = mu[i][0] * delx + mu[i][1] * dely + mu[i][2] * delz;
            pjdotr = mu[j][0] * delx + mu[j][1] * dely + mu[j][2] * delz;

            afac = 1.0 - rsq * rsq * rcutcoul2inv * rcutcoul2inv;
            pre1 = afac * (pdotp - 3.0 * r2inv * pidotr * pjdotr);
            aforcecoulx = pre1 * delx;
            aforcecouly = pre1 * dely;
            aforcecoulz = pre1 * delz;

            bfac = 1.0 - 4.0 * rsq * sqrt(rsq) * rcutcoul2inv * sqrt(rcutcoul2inv) +
                3.0 * rsq * rsq * rcutcoul2inv * rcutcoul2inv;
            presf = 2.0 * r2inv * pidotr * pjdotr;
            bforcecoulx = bfac * (pjdotr * mu[i][0] + pidotr * mu[j][0] - presf * delx);
            bforcecouly = bfac * (pjdotr * mu[i][1] + pidotr * mu[j][1] - presf * dely);
            bforcecoulz = bfac * (pjdotr * mu[i][2] + pidotr * mu[j][2] - presf * delz);

            forcecoulx += 3.0 * r5inv * (aforcecoulx + bforcecoulx);
            forcecouly += 3.0 * r5inv * (aforcecouly + bforcecouly);
            forcecoulz += 3.0 * r5inv * (aforcecoulz + bforcecoulz);

            pre2 = 3.0 * bfac * r5inv * pjdotr;
            pre4 = -bfac * r3inv;

            crossx = pre4 * (mu[i][1] * mu[j][2] - mu[i][2] * mu[j][1]);
            crossy = pre4 * (mu[i][2] * mu[j][0] - mu[i][0] * mu[j][2]);
            crossz = pre4 * (mu[i][0] * mu[j][1] - mu[i][1] * mu[j][0]);

            tixcoul += crossx + pre2 * (mu[i][1] * delz - mu[i][2] * dely);
            tiycoul += crossy + pre2 * (mu[i][2] * delx - mu[i][0] * delz);
            tizcoul += crossz + pre2 * (mu[i][0] * dely - mu[i][1] * delx);
          }

          if (mu[i][3] > 0.0 && q[j] != 0.0) {
            r3inv = r2inv * rinv;
            r5inv = r3inv * r2inv;
            pidotr = mu[i][0] * delx + mu[i][1] * dely + mu[i][2] * delz;
            rcutcoul2inv = 1.0 / cut_coulsq[itype][jtype];
            pre1 = 3.0 * q[j] * r5inv * pidotr * (1 - rsq * rcutcoul2inv);
            pqfac = 1.0 - 3.0 * rsq * rcutcoul2inv +
                2.0 * rsq * sqrt(rsq) * rcutcoul2inv * sqrt(rcutcoul2inv);
            pre2 = q[j] * r3inv * pqfac;

            forcecoulx += pre2 * mu[i][0] - pre1 * delx;
            forcecouly += pre2 * mu[i][1] - pre1 * dely;
            forcecoulz += pre2 * mu[i][2] - pre1 * delz;
            tixcoul += pre2 * (mu[i][1] * delz - mu[i][2] * dely);
            tiycoul += pre2 * (mu[i][2] * delx - mu[i][0] * delz);
            tizcoul += pre2 * (mu[i][0] * dely - mu[i][1] * delx);
          }

          if (mu[j][3] > 0.0 && qtmp != 0.0) {
            r3inv = r2inv * rinv;
            r5inv = r3inv * r2inv;
            pjdotr = mu[j][0] * delx + mu[j][1] * dely + mu[j][2] * delz;
            rcutcoul2inv = 1.0 / cut_coulsq[itype][jtype];
            pre1 = 3.0 * qtmp * r5inv * pjdotr * (1 - rsq * rcutcoul2inv);
            qpfac = 1.0 - 3.0 * rsq * rcutcoul2inv +
                2.0 * rsq * sqrt(rsq) * rcutcoul2inv * sqrt(rcutcoul2inv);
            pre2 = qtmp * r3inv * qpfac;

            forcecoulx += pre1 * delx - pre2 * mu[j][0];
            forcecouly += pre1 * dely - pre2 * mu[j][1];
            forcecoulz += pre1 * delz - pre2 * mu[j][2];
          }
        }

        // LJ interaction

        if (rsq < cut_ljsq[itype][jtype]) {
          r6inv = r2inv * r2inv * r2inv;
          forceljcut = r6inv * (lj1[itype][jtype] * r6inv - lj2[itype][jtype]) * r2inv;

          rcutlj2inv = 1.0 / cut_ljsq[itype][jtype];
          rcutlj6inv = rcutlj2inv * rcutlj2inv * rcutlj2inv;
          forceljsf =
              (lj1[itype][jtype] * rcutlj6inv - lj2[itype][jtype]) * rcutlj6inv * rcutlj2inv;

          forcelj = factor_lj * (forceljcut - forceljsf);
        } else
          forcelj = 0.0;

        // total force

        fq = factor_coul * qqrd2e;
        fx = fq * forcecoulx + delx * forcelj;
        fy = fq * forcecouly + dely * forcelj;
        fz = fq * forcecoulz + delz * forcelj;

        // force & torque accumulation

        f[i][0] += fx;
        f[i][1] += fy;
        f[i][2] += fz;
        torque[i][0] += fq * tixcoul;
        torque[i][1] += fq * tiycoul;
        torque[i][2] += fq * tizcoul;

        if (eflag) {
          if (rsq < cut_coulsq[itype][jtype]) {
            ecoul = qtmp * q[j] * rinv * pow((1.0 - sqrt(rsq) / sqrt(cut_coulsq[itype][jtype])), 2);
            if (mu[i][3] > 0.0 && mu[j][3] > 0.0)
              ecoul += bfac * (r3inv * pdotp - 3.0 * r5inv * pidotr * pjdotr);
            if (mu[i][3] > 0.0 && q[j] != 0.0) ecoul += -q[j] * r3inv * pqfac * pidotr;
            if (mu[j][3] > 0.0 && qtmp != 0.0) ecoul += qtmp * r3inv * qpfac * pjdotr;
            ecoul *= factor_coul * qqrd2e;
          } else
            ecoul = 0.0;

          if (rsq < cut_ljsq[itype][jtype]) {
            evdwl = r6inv * (lj3[itype][jtype] * r6inv - lj4[itype][jtype]) +
                rcutlj6inv * (6 * lj3[itype][jtype] * rcutlj6inv - 3 * lj4[itype][jtype]) * rsq *
                    rcutlj2inv +
                rcutlj6inv * (-7 * lj3[itype][jtype] * rcutlj6inv + 4 * lj4[itype][jtype]);
            evdwl *= factor_lj;
          } else
            evdwl = 0.0;
        }

        if (evflag) ev_tally_xyz_full(i, evdwl, ecoul, fx, fy, fz, delx, dely, delz);
      }
    }
  }
}
